The invention is directed to an electrostatic paint spray gun comprising a built-in high-voltage generator that is composed of a transformer and a high-voltage cascade extending in the gun barrel, whereby a low-voltage input of the cascade is connected to the transformer output and a high-voltage output is connected to the high-voltage electrode of the gun with a stranded lead, and whereby the transformer and cascade are cast into an insulating member. Such paint spray guns have been known for a long time and are commercially available.
In these known electrostatic paint spray guns, a ring transformer is fed with the voltage coming from the mains or, respectively, from the power pack means, the high-voltage output of this ring transformer being in communication with the first stage of a high-voltage cascade, whereby that end of the cascade remote from the ring transformer forms the high-voltage output and is in communication with the high-voltage electrode of the gun via a line. The cascade is thereby generally constructed such that it comprises two columns of capacitors and a corresponding row of diodes lying respectively opposite one another. The high-voltage output of the cascade is connected to helically arranged resistors and to an insulated line, namely, to the stranded lead that leads to the high-voltage electrode, whereby that region of the stranded lead neighboring the high-voltage output is helically wound. The transformer, the high-voltage cascade, the resistors and the helically wound stranded part are cast out with a casting compound and thus embedded in an insulating member that usually has a cylindrical shape. As known, however, care must be exercised in the manufacture of the insulating member to see that the curing temperature for the casting compound does not go above 58.degree. C. because the insulating hose of the co-cast stranded region does not withstand a higher temperature. Expressed in other terms, there is a non-compatibility between the insulating hose and the casting compound, namely, to the effect that they have different temperature shrink behavior, with the consequence that a gap is formed at least over sub-regions between the insulating hose and the cured casting compound given too high a curing temperature, this, as experience has taught, leading to breakdowns. This necessarily results in a high reject rate in the manufacture of such cascades.